Bearing the Brunt

High-Performance Brake Pads Add Stopping Power

What's the most important part of an automobile's braking system? Granted, every component in this area is vital, from pedal to rotor as well as the lines, hoses, hydraulic fluid, boosters, proportioning valves, antilock systems, and calipers in between. If any piece malfunctions, the entire system is adversely affected, and stopping is no longer a given. But assuming that everything is working properly, we ask again, what part of a braking system is most important? We submit that the lowly brake pad is right up at the top of the list. Braking, as you know, is a matter of friction--to paraphrase our overview piece, a vehicle's forward momentum is counteracted by the frictional forces created when its brake pads are clamped down onto a brake rotor. Where the pad meets the rotor is where braking happens, and installing high-performance brake pads can make for quicker, more consistent stops.

The stresses at this flash point are enormous, and brake pad >> engineers have a lot of variables to balance. Friction generates heat, which is a necessary by-product of brake action, but also the number one enemy of good and consistent braking. The more friction during braking the better the stopping, but how a pad handles the resultant heat is critical to brake system performance. Gas is also created, and must be evacuated, as the resin that holds the brake pad material together is broken down. There's also the problem of shear forces, as the spinning rotor attempts to rip the pad material from its backing plate. We don't need to explain why that would be bad. Then, in a street-driven car at least, there are the issues of brake noise and pad and rotor wear.

Disc brake pads, for the most part, are compromises. With a common OEM-style pad, friction, and therefore stopping power, is compromised in favor of low noise, low wear, and low dust levels. Competition pads are compromised in the other direction; noise and dust are irrelevant, and the pads only have to last as long as the race does. In this age, though, the level of innovation, technology, and engineering put into high-performance street-going brake pads means that super stopping power comes with acceptable levels of noise, dusting, and wear.

"Installing a set of high-performance brake pads," says Jerry DeMarino of Hawk Performance, "is the single biggest improvement someone can make to their car's brake system." This is even more so, according to DeMarino, if said car is wearing sticky, larger-than-stock tires, since the extra "stick" creates more heat in the brake system.

No longer do brake engineers talk about "hard" or "soft" pads; instead, they measure pad material's compressibility. More compressibility means less "feel" at the pedal, and vice versa. Most brake manufacturers are also heavily focused on tribology, which is "the study of the design, friction, wear, and lubrication of interacting surfaces in relative motion." (Thanks, Webster's.) The result of this research is that most high-performance pads generate a transfer film onto the rotor during the bedding-in process. (Most hi-po pads require heat cycling before they're ready for serious use--for example, this writer's aftermarket pads were smoking during the prescribed bedding-in ritual.) The transfer film creates adhesive friction, i.e., pad and rotor adhere to each other during stopping, in addition to the abrasive friction created when the pad is forced against the rotor by the caliper. At the same time, this layer acts as a buffer, since the pad isn't actually contacting the rotor. Response, wear, feel, and consistency are improved.

All that, and we haven't even gotten into brake pad materials. The classifications "metallic," "semi-metallic," and "organic" used to suffice; now they seem a bit limiting. With one exception, the pads we're showing you here can generally be classified as semi-metallic pads, which contain less than 75 percent metallic content. This is where innovations in pad technology are happening, because the non-metallic content can consist of just about anything: carbon, ceramics, Kevlar and other undisclosed unobtaniums. The proprietary formulas are nearly endless, though new classifications such as "carbon-metallic" and "carbon-ceramic" have come into vogue. For example, Hawk Performance's Ferro-Carbon High Performance Street pads are made up of organic, ceramic, metallic, and carbon fiber materials. All the manufacturers shown here have their own witch's brews that provide wicked >> stopping power along with civilized street manners.

Now, we know many of you still run drum brakes, especially on the rear of your Chevys. The simple fact, though, is that drum brake innovations are far and few between. The Master Power big-drum install you'll find elsewhere in this issue utilizes high-tech matrix ceramic shoes; Praise Dyno Brake (www.praisedynobrake.com, 972/ 636-2722) cryogenically treats its drums and shoes, a process they claim makes brake material more dense than stock material, which improves dissipation of heat, therefore increasing performance and extending the wear. Disc systems, however, are the present and the future of high-performance braking, so that's what we've concentrated on here.

We've thrown a lot of engineering gobbledygook at you in a short space, but here it is in a nutshell: never have so many companies invested so much time, money, and research into enabling performance enthusiasts to stop faster, better, and more consistently. One of the manufacturers featured claims 20-40 percent more stopping power with high resistance to fade; another quotes consistent 12-feet reductions in 60-0 stopping distances over OEM pads. Better brake performance, and all the benefits that come with it, may be no further away than a simple pad change away.

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Bearing the Brunt

1a-b. All the high-performance brake pad manufacturers featured in this story subject their offerings to rigorous testing, from torture sessions on a brake dyno, to race and road testing, right down to state-of-the-art computer analysis that looks at friction material on a molecular level. (Photos courtesy of SBS.)

1b.

2. Most, if not all high-performance disc brake pads are designed to work with a transfer film on the rotor surface. Created during the pad bedding procedure, this layer of friction material serves a number of purposes: it makes for a better mating surface for the pad, improves pedal response and braking consistency, and even acts as a buffer between pad and rotor, allowing it to wear longer and more evenly. (Photo courtesy of SBS

3. Note how the slots in this disc brake pad have been clogged with friction material. When a slotted disc brake pad reaches this point, it's time to consider an upgrade to better pads. (Photo courtesy of SBS.)

4a-b. EBC Brakes color-codes its offerings. Greenstuff features an organic compound that claims to greatly reduce brake dust while maintaining a high level of friction; Redstuff comes in a semi-metallic version created with Detroit muscle in mind, and a ceramic compound version formulated for track-day use.

7. SBS (Scandinavian Brake Systems) pads for the street come in two versions: the ceramic compound Pro Touring version, and the carbon-ceramic compound Pro Track type. Both claim to eliminate brake fade, keep rotor wear low, and have rising friction levels toward the end of a stop. Pro Touring pads keep the dust and noise low, while Pro Track pads feature a high level of initial bite. Advanced technologies in the areas of pad retention, pad degassing, and material blending are also used.

8. Wilwood is one of the newest entrants in the performance brake pad market with its PolyMatrix brand. These pads claim a "unique balance" of abrasive and adhesive friction elements to provide superior stopping power without undue rotor wear. Wilwood's Nucap Retention System consists of hook-like steel projections on the backing plate that are molded into the friction material to create a virtually one-piece unit. Compounds "E", "D", "Q", and "T" are appropriate for various types of performance street use.